J2se Network Programming

I. Network Basics

Network Communication Protocol: for speed and transmissionCodeCode structure, transmission control steps, error control, and other standards.

Network Communication Interface: hardware device: Implements information transmission between nodes.

Software device: Agreement for communications between the parties.

 

 

 

 

Software developers should master the layer-4 model on the right.

Ii. TCP/IP protocol

IP protocol: provides unique IP addresses.

-| IPv4

Subnet Mask

Gateway

-| IPv6

TCP: a connection-oriented protocol. Reliable, end-to-end byte stream communication protocol. Byte stream.

That is, data can be transmitted in place. Data Packets arrive in order without any disordered order. Such as phone number.

Relatively low efficiency than UDP

UDP: a method for sending encapsulated original IP datagram, and no connection is required during sending. Is an unreliable connection.

Only sends data, regardless of whether the recipient receives the data. Such as a telegram.

 

TCP is reliable and slow.

UDP is not reliable, fast, and efficient.

 

Iii. Socket

1. Used for client-server connection

2. The two socket classes and serversocket classes defined in the java.net package are respectively used to implement two-way connection between the client and server.

3. The addressing information required for establishing a connection is the IP address and port number of the remote computer (port number after 1024 during development)

-| The TCP port is different from the UDP port.

Each port has 65536 ports.

 Import  Java. Io. datainputstream;  Import  Java. Io. ioexception;  Import  Java.net. serversocket;  Import  Java.net. Socket;  Public  Class  Tcpserver {  Public   Static   Void Main (string ARGs []) Throws  Ioexception {serversocket SS = New Serversocket (6666 );  While ( True  ) {Socket s = SS. Accept (); datainputstream dis =New  Datainputstream (S. getinputstream (); system. Out. println (DIS. readutf (); DIS. Close (); S. Close ();}}}  Import  Java. Io. dataoutputstream;  Import  Java. Io. ioexception;  Import  Java. Io. outputstream;  Import  Java.net. Socket;  Import  Java.net. unknownhostexception;  Public  Class  Tcpclient {  Public   Static   Void Main (string ARGs []) Throws  Unknownhostexception, ioexception {socket s = New Socket ("127.0.0.1", 6666 ); Outputstream OS = S. getoutputstream (); dataoutputstream DoS = New  Dataoutputstream (OS); dos. writeutf ( "Hello gay! "); Dos. Flush (); dos. Close (); S. Close ();}}